Chromeno[4,3,2-de]isoquinolines as potent dopamine receptor ligands

ABSTRACT

Novel dopamine receptor ligands of the formula: 
                 
 
pharmaceutical formulations of such compounds, and a method using such compounds for treating a patient suffering from dopamine-related dysfunction of the central or peripheral nervous system, are described. The compounds are expected to be useful in treating Parkinson&#39;s disease, improving cognition, improving memory, improving the negative symptoms of schizophrenia, improving attention-deficit hyperactivity disorder and related developmental disorders, treating substance abuse disorders, and in treating various peripheral conditions where changes in dopamine receptor occupation affects physiological function, including organ perfusion, cardiovascular function, and selected endocrine and immune system functions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 09/598,127, filed on Jun. 21, 2000, now U.S. Pat.No. 6,413,977, which claims priority to U.S. Provisional ApplicationSer. No. 60/140,166, filed on Jun. 21, 1999.

GOVERNMENT RIGHTS CLAUSE

This invention was made with Government support under Grant No. MH42705awarded by the National Institute of Health. The Government has certainrights in the invention.

FIELD OF THE INVENTION

This invention is directed to novel ligands for dopamine receptors. Moreparticularly, the present invention is directed to optionallysubstituted 1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinoline compoundsand their use in pharmaceutical formulations for treatment ofdopamine-related dysfunction of the central and peripheral nervoussystem.

BACKGROUND AND SUMMARY OF THE INVENTION

Dopamine, a neurotransmitter in the central nervous system, has beenimplicated in numerous neurological disorders. For example, it has beenhypothesized that excess stimulation of dopamine receptor subtypes maybe linked to schizophrenia. Additionally, it is generally recognizedthat either excessive or insufficient functional dopaminergic activityin the central and/or peripheral nervous system may cause hypertension,narcolepsy, and other behavioral, neurological, physiological, andmovement disorders including Parkinson's disease, a chronic, progressivedisease characterized by an inability to control the voluntary motorsystem.

Dopamine receptors have traditionally been classified into two families(the D₁ and D₂ dopamine receptor families) based on pharmacological andfunctional evidence. D₁ receptors preferentially recognize thephenyltetrahydrobenzazepines and generally lead to stimulation of theenzyme adenylate cyclase, whereas D₂ receptors recognize thebutyrophenones and benzamides and often are coupled negatively (or notat all) to adenylate cyclase. It is now known that at least five genesexist that code for subtypes of dopamine receptors: the D₁, D₂, D₃, D₄and D₅ receptor subtypes. The traditional classification, however,remains useful, with the D₁-like class comprising the D₁ (D_(1A)) andthe D₅ (D_(1B)) receptor subtypes, whereas the D₂-like class consists ofthe D₂, D₃ and D₄ receptor subtypes. Variation can occur also throughsplice variants (e.g., the D_(2L) and D_(2S) splice variants), as wellas through different alleles (e.g., multiple repeats of the D₄ gene).

Central nervous system drugs exhibiting affinity for the dopaminereceptors are generally classified not only by their receptorselectivity, but further by their agonist (receptor activating) orantagonist (receptor blocking) activity. While the physiologicalactivities associated with the interaction of dopamine with the variousreceptor subtypes are not fully understood, it is known that ligandsexhibiting selectivity for a particular receptor subtype will producemore or less predicable neuropharmacological results. The availabilityof selective dopamine receptor antagonist and agonist compounds permitsthe design of experiments to enhance understanding of the manyfunctional roles of D₁ receptors and can lead to new treatments forvarious central and peripheral nervous system disorders. In addition, ifagonists were available with high affinity for both the D₁ and D₂receptors, these agonists could be used under circumstances wherebinding to both D₁ and D₂ receptors is beneficial.

The early focus of dopamine receptor studies was on the D₂ family, but acritical role of the dopamine D₁ receptor in nervous system function hasbecome apparent recently. That early work on selective D₁ receptorligands primarily focused on molecules from a single chemical class, thephenyltetrahydrobenzazepines, such as the antagonist SCH23390 (1):

Several of the phenyltetrahydrobenzazepines were found to be D₁ receptoragonists; however, the agonists derived from this class [including, forexample, SKF38393 (+)-2] generally were partial agonists. Even SKF82958,purported to be a full agonist, recently has been shown not to have fullintrinsic efficacy in preparations with decreased receptor reserve. Thedifferentiation between D₁ agonists of full and partial efficacy isimportant to the medical research community because this may influencethe actions of these compounds on complex central nervous systemmediated events. For example, two full agonists (dihydrexidine andA-77636) have exceptional antiparkinsonian effects in the MPTP-treatedmonkey model, whereas partial agonists are without significant activity.More recent data suggest that full and partial agonists also differ intheir effects on other complex neural functions. In addition, there arereceptor-mediated events (e.g., recruitment of G proteins and associatedreceptor kinases) that can affect agonist activity. These latterbiochemical events may occur independently of the changes in secondmessenger levels (e.g., cAMP) mediated by a drug.

Accordingly, researchers have directed their efforts to design ligandsthat are full agonists (i.e., have full intrinsic efficacy) for the D₁receptor. One such compound is dihydrexidine (3), ahexahydrobenzo[a]phenanthridine of the formula:

The structure of dihydrexidine (3) is unique from other D₁ agonistsbecause the accessory ring system is tethered, making the moleculerelatively rigid. Molecular modeling studies of dihydrexidine (3) haveshown that the compound has a limited number of low energyconformations, and the aromatic rings are held in a relatively coplanararrangement in all of these conformations. The recent elucidation of theconfiguration of the active enantiomer of dihydrexidine (3) wasconsistent with predictions from this model.

Unlike other high affinity, high intrinsic activity D₁ agonists like3-substituted aminomethylisochromans, dihydrexidine (3) provided asemi-rigid template for developing a dopamine ligand model. Theessential features of this model include the presence of a transoidβ-phenyldopamine moiety, an equatorially oriented electron lone pair onthe basic nitrogen atom, and near coplanarity of the pendant phenyl ringwith the catechol ring. The dihydrexidine-based model has a transoidβ-phenyldopamine moiety, whereas the dopaminergicphenyltetrahydrobenzazepines have a cisoid β-phenyldopamineconformation. The dihydrexidine-based model has served as the basis forthe design of additional D₁ receptor agonists. The design and synthesisof D₁ receptor agonists having high intrinsic activity is important tothe medical research community due to the potential use of full agoniststo treat complex central nervous system mediated events, and alsoconditions in which peripheral dopamine receptors are involved. Forexample, the compositions of the present invention have potential use asagents for lowering blood pressure, and for affecting lung and kidneyfunction.

One embodiment of the present invention is a novel class of dopaminereceptor agonists of the general formula:

and pharmaceutically acceptable salts thereof, and pharmaceuticalformulations of such compounds. The present compounds are useful fortreating patients having a dopamine-related dysfunction of the centralnervous system (as evidenced by an apparent neurological, psychological,physiological, or behavioral disorder), as well as conditions in whichperipheral dopamine receptors are involved (including target tissuessuch as the kidney, lung, endocrine, and cardiovascular systems).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of the affinity of dinoxyline(circles), dinapsoline (diamonds) and (+)-SCH23390 (solid circles) forstriatal D₁ receptors. Rat striatal D₁ receptors were labeled with[³H]SCH23390 (1), and unlabeled dinoxyline, dinapsoline, or (+)-SCH23390was added to determine the specific binding of each compound to the D₁receptor.

FIG. 2 is a graphic representation of the affinity of dinoxyline(circles), dinapsoline (diamonds) and (+)-SCH23390 (solid circles) forprimate D₁ receptors expressed in C-6 cells. D₁ receptors were labeledwith [³H]SCH23390 (1), and unlabeled dinoxyline, dinapsoline, or(+)-SCH23390 was added to determine the specific binding of eachcompound to the D₁ receptor.

FIG. 3 is a graphic representation of the affinity of dinoxyline(circles), dinapsoline (diamonds), and chlorpromazine for striatal D₂receptors labeled with [³H]spiperone. Unlabeled dinoxyline, dinapsoline,or chlorpromazine was added to determine the specific binding of eachcompound to the D₂ receptor.

FIG. 4 is a graphic representation of the number of contralateralrotations over time (hours) in rats treated in the unilateral 6-OHDAlesion model with dinoxyline (squares) or dihydrexidine (circles).

DETAILED DESCRIPTION OF THE INVENTION

There is provided in accordance with the present invention a compound ofthe general formula:

and pharmaceutically acceptable salts thereof wherein R₁-R₃ arehydrogen, C₁-C₄ alkyl or C₂-C₂₄ alkenyl; R₈ is hydrogen, C₁-C₄ alkyl ora phenoxy protecting group; X₉ is hydrogen, halo including chloro,fluoro and bromo, or a group of the formula —OR wherein R is hydrogen,C₁-C₄ alkyl or a phenoxy protecting group, and R₄, R₅ and R₆ areindependently selected from the group consisting of hydrogen, C₁-C₄alkyl, phenyl, halo, or a group —OR wherein R is as defined above, andwhen X₉ is a group of the formula —OR, the groups R₈ and R can be takentogether to form a group of the formula —CH₂—.

The term “C₂-C₂₄ alkenyl” refers to allyl, 2-butenyl, 3-butenyl, andvinyl.

The term “C₁-C₄ alkyl” as used herein refers to branched or straightchain alkyl groups comprising one to four carbon atoms, including, butnot limited to, methyl, ethyl, propyl, isopropyl, n-butyl, t-butyl andcyclopropylmethyl.

In one embodiment at least one of R₄, R₅ or R₆ is hydrogen. In anotherembodiment at least two of R₄, R₅ or R₆ is hydrogen.

The term “pharmaceutically acceptable salts” refers to those saltsformed using organic or inorganic acids which salts are suitable for usein humans and lower animals without undesirable toxicity, irritation,allergic response and the like. Acids suitable for formingpharmaceutically acceptable salts of biologically active compoundshaving amine functionability are well known in the art. The salts can beprepared according to conventional methods in situ during the finalisolation and purification of the present compounds, or separately byreacting the isolated compounds in free base form with a suitable saltforming acid.

The term “phenoxy protecting group” as used herein refers tosubstituents on the phenolic oxygen which prevent undesired reactionsand degradations during synthesis and which can be removed later withouteffect on other functional groups on the molecule. Such protectinggroups and the methods for their application and removal are well knownin the art. They include ethers, such as cyclopropylmethyl, cyclohexyl,allyl ethers and the like; alkoxyalkyl ethers such as methoxymethyl ormethoxyethoxymethyl ethers and the like; alkylthioalkyl ethers such asmethylthiomethyl ethers; tetrahydropyranyl ethers; arylalkyl ethers suchas benzyl, o-nitrobenzyl, p-methoxybenzyl, 9-anthrylmethyl, 4-picolylethers and the like; trialkylsilyl ethers such as trimethylsilyl,triethylsilyl, t-butyldimethylsilyl, t-butyldiphenylsilyl ethers and thelike; alkyl and aryl esters such as acetates, propionates, butyrates,isobutyrates, trimethylacetates, benzoates and the like; carbonates suchas methyl, ethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, benzyland the like; and carbamates such as methyl, isobutyl, phenyl, benzyl,dimethyl and the like.

The term “C₁-C₄ alkoxy” as used herein refers to branched or straightchain alkyl groups comprising one to four carbon atoms bonded through anoxygen atom, including but not limited to, methoxy, ethoxy, propoxy andt-butoxy.

Further, in accordance with other embodiments of this invention thepresent compounds can be formulated in conventional drug dosage formsfor use in methods for treating a patient suffering fromdopamine-related dysfunction of the central or peripheral nervoussystem. Effective doses of the present compounds depend on many factors,including the indication being treated, the route of administration, andthe overall condition of the patient. For oral administration, forexample, effective doses of the present compounds are expected to rangefrom about 0.1 to about 50 mg/kg, more typically about 0.5 to about 25mg/kg. Effective parenteral doses can range from about 0.01 to about 5mg/kg of body weight. In general, treatment regimens utilizing compoundsin accordance with the present invention comprise administration of fromabout 1 mg to about 500 mg of the compounds of this invention per day inmultiple doses or in a single dose.

Liquid dosage forms for oral administration may include pharmaceuticallyacceptable emulsions, microemulsions, solutions, suspensions, and syrupscontaining inert diluents commonly used in the art, such as water. Suchcompositions may also comprise adjuvants such as wetting agents,emulsifying and suspending agents, sweetening, and flavoring agents.Injectable preparations of the compounds of the present invention can beformulated utilizing art-recognized products by dispersing or dissolvingan effective dose of the compound in a parenterally acceptable diluentsuch as water, or more preferably isotonic sodium chloride solution. Theparenteral formulations can be sterilized using art-recognizedmicrofiltration techniques.

The compounds of this invention can also be formulated as solid dosageforms for oral administration such as capsules, tablets, powders, pillsand the like. Typically the active compound is admixed with an inertdiluent or carrier such as sugar or starch and other excipientsappropriate for the dosage form. Thus, tableting formulations willinclude acceptable lubricants, binders and/or disintegrants. Optionallypowder compositions comprising an active compound of this invention and,for example, a starch or sugar carrier can be filled into gelatincapsules for oral administration. Other dosage forms of the compounds ofthe present invention can be formulated using art-recognized techniquesin forms adapted for the specific mode of administration.

One compound provided in accordance with the present invention is(±)-8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinolinehydrobromide denominated hereinafter as “dinoxyline.” Dinoxyline issynthesized from 2,3-dimethoxyphenol, as depicted in Scheme 1. Thephenolic group is protected as the methoxymethyl (“MOM”) derivativefollowed by treatment with butyllithium, then with the substitutedborolane illustrated, to afford the borolane derivative 2.

As shown in Scheme 1, this borolane derivative is then employed in aPd-catalyzed Suzuki type cross coupling reaction with5-nitro-4-bromoisoquinoline. The resulting coupling product 4 is thentreated with toluenesulfonic acid in methanol to remove the MOMprotecting group of the phenol. Simple treatment of this nitrophenol 5with potassium carbonate in DMF at 80° C. leads to ring closure withloss of the nitro group, affording the basic tetracyclicchromenoisoquinoline nucleus 6. Simple catalytic hydrogenation causesreduction of the nitrogen-containing ring to yield 7. Use of borontribromide to cleave the methyl ether linkages gives the parent compound8.

It is apparent that by appropriate substitution on the isoquinoline ringa wide variety of substituted compounds can be obtained. Substitutiononto the nitrogen atom in either 6 or 7, followed by reduction willreadily afford a series of compounds substituted with lower alkyl groupson the nitrogen atom. Likewise, the use of alkyl substituents on the 1,3, 6, 7, or 8 positions of the nitroisoquinoline 3 would lead to avariety of ring-substituted compounds. In addition, the 3-position of 6can also be directly substituted with a variety of alkyl groups.Similarly, replacement of the 4-methoxy group of 2, in Scheme 1, withfluoro, chloro, or alkyl groups leads to the subject compounds withvariations at X₉. When groups are present on the nucleus that are notstable to the catalytic hydrogenation conditions used to convert 6 to 7,we have found that reduction can be accomplished using sodiumcyanoborohydride at slightly acidic pH. Further, formation of theN-alkyl quaternary salts of derivatives of 6 gives compounds that arealso easily reduced with sodium borohydride, leading to derivatives of7.

Space-filling representations of the low energy conformations for(+)-trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a]phenanthridine[(+)-dihydrexidine] and the 11bR enantiomer of dinoxyline that ishomochiral to (+)-dihydrexidine at its 12bS chiral center have beencompared. Two major structural features are readily evident. First, thesteric bulk provided by the C(7)-C(8) ethano bridge in dihydrexidine (3)has been removed. Second, the angle of the pendent

Scheme 1. Scheme for the synthesis of8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinolinehydrobromide phenyl ring with respect to the plane of the catechol ringis changed slightly. This is most evident, in face-on views, where thearomatic hydrogen H(1) in dihydrexidine (3) projects above the catecholring. In dinoxyline however, this position is used to tether the pendentphenyl ring through an oxygen atom, to the catechol ring; this forcesthe pendent phenyl ring to twist in a clockwise direction, relative todihydrexidine (3), when viewed from above. The amino groups are insimilar positions, given the degree of conformational flexibility of theheterocyclic rings. In addition, both molecules can present an N—Hvector in an equatorial orientation, a feature of the pharmacophorebelieved to be important for D₁ receptor agonists. Consistent with thoseobservations the pharmacological properties of these two molecules aresimilar.

Experiments have been conducted to determine the binding of dinoxylineat D₁ receptors. Dinoxyline was found to have similar affinity(K_(0.5)<5 nM) to dinapsoline for rat striatal D₁ receptors. Inaddition, competition experiments utilizing unlabeled SCH23390 (1) as acompetitor demonstrated that dinoxyline competes with high affinity,having a shallow competition curve (n_(H)=ca. 0.7) consistent withagonist properties (see FIGS. 1 and 2). The agonist properties ofdinoxyline at D₁ receptors were confirmed in vitro by measuring theability of dinoxyline to increase cAMP production in rat striatum andC-6-mD₁ cells. In both rat striatum and C-6-mD₁ cells, dinoxyline hasfull agonist activity with an EC₅₀ of less than 30 nM in stimulatingsynthesis of cAMP via D₁ receptors.

Thus, the pharmacological data confirm that dinoxyline has high affinityfor dopamine D₁ receptors labeled with [³H]SCH23390 that is slightlygreater than that of(+)-trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a]phenanthridine(dihydrexidine 3). Moreover, dinoxyline, in both rat striatal membranesand in cloned expressed primate D_(1A) receptors, was a full agonistrelative to dopamine, similar to dihydrexidine (3) but unlike thepartial agonist (+)-SKF 38393 (see FIGS. 2 and 3: (+)-SKF 38393=(+)-2;(±)-trans-10,11-dihydroxy-5,6,6a,7,8,12b-hexahydrobenzo[a]phenanthridine=(±)-3,and(±)-8,9-dihydroxy-2,3,7,11b-tetrahydro-1H-naphtho[1,2,3-de]isoquinoline=4;dinapsoline).

Based on the underlying model of the D₁ pharmacophore, it is anticipatedthat both the affinity and intrinsic activity of racemic dinoxyline (andsubstituted analogs thereof) reside in only one of its enantiomers—the11bR absolute configuration (and its homochiral analogs). Resolution ofthe racemate using art recognized separation techniques is expected toyield one dinoxyline isomer with approximately twice the D₁ affinityexhibited by the racemate.

Dihydrexidine was determined to be about ten-fold D₁:D₂ selective. Inaddition, dihydrexidine, while having the expected dopamine agonistactivity, also had an unusual property termed herein as “functionalselectivity”. Specifically, in rats (in vivo or in vitro), dihydrexidineacts as an agonist at D₂-like receptors located post-synaptically, butas an antagonist at D₂-like receptors located pre-synaptically. Such isbelieved to be due to differences in the ligand-receptor-G proteincomplex located post-synaptically vs. pre-synaptically, as determined bythe specific G proteins present in the given cellular milieu. As shownin FIG. 1 and Table 1, dinoxyline has greater affinity for D₂-likereceptors than does dihydrexidine, providing the first full agonisthaving very high affinity for both D₁ and D₂ receptors in mammalianbrain. Moreover, dinoxyline differs from dihydrexidine in its(“functional selectivity” properties.

It has been shown that these D₂ properties of dihydrexidine reside inthe same enantiomer (i.e., 6aR, 12bS) that is the high affinity fullagonist at the D₁ receptor. On this basis, it is expected that both theD₁ and D₂ properties of dinoxyline also reside in the homochiralenantiomer. The optical isomers of dinoxyline, and appropriate analogs,constitute significant tools to study the phenomena of “functionalselectivity”.

The antiparkinsonian effects of dihydrexidine in the MPTP model ofParkinson's disease have been previously reported, and it is anticipatedthat dinoxyline will show similar effects. As shown in FIG. 4,dinoxyline has been tested in the rat unilateral 6-OHDA-lesion model, aparadigm that shows in vivo dopamine agonist activity, and has beenproposed by some to predict antiparkinson drug efficacy. As can be seen,dinoxyline causes significant rotation that persists for approximatelyfive hours after a single subcutaneous dose. This is more than twice theduration of action of a similar dose of dihydrexidine administered bythe same route. Consistent with these data, preliminary studies havealso been performed in marmosets having moderately-severe MPTP-induceddopamine denervation. Dinoxyline was found to have significantantiparkinson effects, causing an increase in locomotion and arousal,and a decrease in Parkinson signs. Accordingly dinoxyline and itsderivatives have potential clinical utility in Parkinson's Disease andin other conditions where perturbation of dopamine receptors may betherapeutic. In addition, it has been reported that appropriatemodification of dihydrexidine will produce analogs that can be targetedto specific subpopulations of the dopamine receptor family. Whereassimilar strategies with dinoxyline should result in compounds with novelreceptor subtype selectivity and/or functional profiles, the effect ofthese substitutions is not the same as with the dihydrexidine backbone.

Dopamine itself is seldom used as a drug because although it activatesall dopamine receptors, it must be given intravenously, it has a veryshort pharmacokinetic half-life, and it also can activate othermonoamine receptors. This series differs from earlier rigid dopamineanalogs in several important ways. First, this is the first series ofhigh affinity full D₁ agonists that also has at least equally highaffinity for D₂ receptors. Thus, whereas dihydrexidine is ten-fold D₁:D₂selective and dinapsoline is five-fold D₁:D₂ selective, dinoxylineactually has equally high affinity for both receptors. In the twoearlier series, it was possible to increase the D₂ affinity, but only atthe expense of D₁ affinity. This series provides the ability to havedrugs with high affinity for both populations of receptors. Drugs withhigh affinity simultaneously for both the D₁ and D₂ offer specificclinical advantages over agents with high affinity for only one of themajor families. The novelty of this series is clearer when theinteraction with the specific dopamine receptor isoforms is examined. Animportant difference between this series and earlier drugs likedihydrexidine and dinapsoline is that those agents had essentially noaffinity for the D₄ receptor isoform. Conversely, dinoxyline has aK_(0.5) of less than 45 nM at the cloned human D₄ receptor, as comparedto >1,000 for either dinapsoline or dihyrexidine or their derivatives.Although D₄ antagonists have been shown to lack efficacy in treatingschizophrenia, there is great potential for the use of high efficacy D₄agonists for selected psychiatric and neurological illnesses.

Another major difference with this series is the effect of substituentson receptor activity. It would have been predicted based on availabledata with dihydrexidine that N-propyl or N-allyl additions wouldmarkedly increase the D₂ affinity of the parent ligands. In fact, theseN-substituents decreased the D₂ affinity of the parent compoundsignificantly. This dramatic difference suggests that dinoxyline isbinding to the D₂ receptor in an unexpected way, and should have uniquetherapeutic utility as well.

With reference to the following described experimental procedures,melting points were determined with a Thomas-Hoover melting pointapparatus and are uncorrected. ¹H NMR spectra were recorded with aVarian VXR 500S (500 MHZ) NMR instrument and chemical shifts werereported in values (ppm) relative to TMS. The IR spectra were recordedas KBr pellets or as a liquid film with a Perkin Elmer 1600 series FTIRspectrometer. Chemical ionization mass spectra (CIMS) were recorded on aFinnigan 4000 quadruple mass spectrometer. High resolution CI spectrawere recorded using a Kratos MS50 spectrometer. Elemental analysis datawere obtained from the microanalytical laboratory of Purdue University,West Lafayette, Ind.

THF was distilled from benzophenone-sodium under nitrogen immediatelybefore use; 1,2-Dichloroethane was distilled from phosphorous pentoxidebefore use.

EXAMPLE 1A Synthesis of8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinolinehydrobromide (Dinoxyline)

1,2-Dimethoxy-3-methoxymethoxybenzene (1).

A slurry of sodium hydride was prepared by adding 1000 ml of dry THF to7.06 g (0.18 mol) of sodium hydride (60% dispersion in mineral oil)under an argon atmosphere at 0° C. To the slurry, 2,3-dimethoxy phenol(23.64 g; 0.153 mol) was added via syringe. The resulting solution wasallowed to warm to room temperature and stirred for two hours. The blacksolution-was cooled to 0° C. and 13.2 ml of chloromethyl methyl ether(14 g; 0.173 mol) was slowly added via syringe. The solution was allowedto reach room temperature and stirred for an additional 8 hours. Theyellow mixture was concentrated to an oil that was dissolved in 1000 mlof diethyl ether. The resulting solution was washed with water (500 ml),2N NaOH (3×400 ml), dried (MgSO₄), filtered, and concentrated. AfterKugelrohr distillation (90-100° C., 0.3 atm), 24.6 g of a clear oil(84%) was obtained: ¹H NMR: (300 MHz, CDCl₃): 6.97 (t, 1H, J=8.7 Hz);6.79 (dd, 1H, J=7.2, 1.8 Hz); 6.62 (dd, 1H, J=6.9, 1.2 Hz); 5.21 (s,2H); 3.87 (s, 3H); 3.85 (s, 3H); 3.51 (s, 3H). CIMS m/z: 199 (M+H⁺,50%); 167 (M+H⁺—CH₃OH, 100%). Anal. Calc'd for C₁₀H₄O₄: C, 60.59; H,7.12. Found: C, 60.93; H, 7.16.

2-(3,4-Dimethoxy-2-methoxymethoxyphenyl)-4,4,5,5-tetramethyl[1,3,2]dioxaborolane(2).

The MOM-protected phenol 1 (10 g; 0.0505 mol) was dissolved 1000 ml ofdry diethyl ether and cooled to −78° C. A solution of n-butyl lithium(22.2 ml of 2.5 M) was then added via syringe. The cooling bath wasremoved and the solution was allowed to warm to room temperature. Afterstirring the solution at room temperature for two hours, a yellowprecipitate was observed. The mixture was cooled to −78° C., and 15 mlof 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.080 mol) wasadded via syringe. The cooling bath was removed after two hours.Stirring was continued for four hours at room temperature. The mixturewas then poured into 300 ml of water and extracted several times withdiethyl ether (3×300 ml), dried (Na₂SO₄), and concentrated to a yellowoil (12.37 g, 76%) that was used without further purification: ¹H NMR:(300 MHz, CDCl₃): 7.46 (d, 1H, J=8.4 Hz); 6.69 (d, 1H, J=8.4 Hz); 5.15(s, 2H); 3.87 (s, 3H); 3.83 (s, 3H); 1.327 (s, 12H).

4-Bromo-5-nitroisoquinoline (3).

Potassium nitrate (5.34 g; 0.052 mol) was added to 20 ml of concentratedsulfuric acid and slowly dissolved by careful heating. The resultingsolution was added dropwise to a solution of 4-bromoisoquinoline (10 g;0.048 mol) dissolved in 40 ml of the same acid at 0° C. After removal ofthe cooling bath, the solution was stirred for one hour at roomtemperature. The reaction mixture was then poured onto crushed ice (400g) and made basic with ammonium hydroxide. The resulting yellowprecipitate was collected by filtration and the filtrate was extractedwith diethyl ether (3×500 ml), dried (Na₂SO₄), and concentrated to givea yellow solid that was combined with the initial precipitate.Recrystallization from methanol gave 12.1 g (89%) of slightly yellowcrystals: mp 172-174° C.; ¹H NMR: (300 MHz, CDCl₃): 9.27 (s, 1H); 8.87(s, 1H); 8.21 (dd, 1H, J=6.6, 1.2 Hz); 7.96 (dd, 1H, J=6.6, 1.2 Hz);7.73 (t, 1H, J=7.5 Hz). CIMS m/z: 253 (M+H⁺, 100%); 255 (M+H⁺+2, 100%).Anal. Calc'd for C₉H₅BrN₂O₂: C, 42.72; H, 1.99; N, 11.07. Found: C,42.59; H, 1.76; N, 10.87.

4-(3,4-Dimethoxy-2-methoxymethoxyphenyl)-5-nitroisoquinoline (4).

Isoquinoline 3 (3.36 g; 0.0143 mol), pinacol boronate ester 2 (5.562 g;0.0172 mol), and 1.0 g (6 mol %) oftetrakis(triphenylphosphine)palladium(0) were suspended in 100 ml ofdimethoxyethane (DME). Potassium hydroxide (3.6 g; 0.064 mol), and 0.46g (10 mol %) of tetrabutylammonium bromide were dissolved in 14.5 ml ofwater and added to the DME mixture. The resulting suspension wasdegassed for 30 minutes with argon and then heated at reflux for fourhours. The resulting black solution was allowed to cool to roomtemperature, poured into 500 ml of water, extracted with diethyl ether(3×500 ml), dried (Na₂SO₄), and concentrated. The product was thenpurified by column chromatography (silica gel, 50% ethyl acetate:hexane) giving 5.29 g of yellow crystals (80.1%): mp 138-140° C.; ¹HNMR: (300 MHz, CDCl₃): 9.33 (s, 1H); 8.61 (s, 1H); 8.24 (dd, 1H, J=7.2,0.9 Hz); 8.0 (dd, 1H, J=6.3, 1.2 Hz); 7.67 (t, 1H, J=7.8 Hz); 7.03 (d,1H, J=9.6 Hz); 6.81 (d, 1H, J=8.1 Hz); 4.86 (d, 1H, J=6 Hz); 4.70 (d,1H, J=5.4 Hz); 3.92 (s, 3H); 3.89 (s, 3H); 2.613 (s, 3H). CIMS m/z: 371(M+H⁺, 100%). Anal Calc'd for C₁₉H₁₈N₂O₆: C, 61.62; H, 4.90; N, 7.56.Found: C, 61.66; H, 4.90; N, 7.56.

2,3-Dimethoxy-6-(5-nitroisoquinolin-4-yl)phenol (5).

After dissolving isoquinoline 4 (5.285 g, 0.014 mol) in 200 ml ofmethanol by gentle heating, p-toluenesulfonic acid monohydrate (8.15 g;0.043 mol) was added in several portions. Stirring was continued forfour hours at room temperature. After completion of the reaction, thesolution was made basic by adding saturated sodium bicarbonate. Theproduct was then extracted with dichlormethane (3×250 ml), dried(Na₂SO₄), and concentrated. The resulting yellow solid (4.65 g; 98%) wasused directly in the next reaction. An analytical sample wasrecrystallized from methanol: mp 170-174° C.; ¹H NMR: (300 MHz, CDCl₃):9.33 (s, 1H); 8.62 (s, 1H); 8.24 (dd, 1H, J=7.2, 0.9 Hz); 7.99 (dd, 1H,J=6.3, 1.2 Hz); 7.67 (t, 1H, J=7.8 Hz); 6.96 (d, 1H, J=8.7 Hz); 6.59 (d,1H, J=8.7 Hz); 5.88 (bs, 1H); 3.94 (s, 3H); 3.92 (s, 3H). CIMS m/z: 327(M+H⁺, 100%). Anal Calc'd for C₁₇H₁₄N₂O₅: C, 62.57; H, 4.32; N, 8.58;Found: C, 62.18; H, 4.38; N, 8.35.

8,9-dimethoxychromeno[4,3,2-de]isoquinoline (6).

Phenol 5 (4.65 g, 0.014 mol) was dissolved in 100 ml of dryN,N-dimethylformamide. The solution was degassed with argon for thirtyminutes. Potassium carbonate (5.80 g, 0.042 mol) was added to the yellowsolution in one portion. After heating at 80° C. for one hour, themixture had turned brown and no more starting material remained. Afterthe solution was cooled to room temperature, 200 ml of water was added.The aqueous layer was extracted with dichloromethane (3×500 ml), thisorganic extract was washed with water (3×500 ml), dried (Na₂SO₄), andconcentrated. A white powder (3.65 g 92%) was obtained that was used inthe next reaction without further purification. An analytical sample wasrecrystallized from ethyl acetate:hexane: mp 195-196° C.; ¹H NMR: (300MHz, CDCl₃): 9.02 (s, 1H); 8.82 (s, 1H); 7.87 (d, 1H, J=8.7 Hz); 7.62(m, 3H); 7.32 (dd, 1H, J=6.0, 1.5 Hz); 6.95 (d, J=9.6 Hz); 3.88 (s, 3H);3.82 (s, 3H). CIMS m/z: 280 (M+H⁺, 100%).

8,9-dimethoxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinoline (7).

Platinum (IV) oxide (200 mg) was added to a solution containing 50 ml ofacetic acid and isoquinoline 6 (1 g; 3.5 mmol). After adding 2.8 ml ofconcentrated HCl, the mixture was shaken on a Parr hydrogenator at 60psi for 24 hours. The green solution was filtered through Celite toremove the catalyst and the majority of the acetic acid was removed byrotary evaporation. The remaining acid was neutralized using a saturatedsodium bicarbonate solution, extracted with diethyl ether (3×250 ml),dried (Na₂SO₄), and concentrated. The resulting oil (0.997 g; 99%) wasused without further purification: ¹H NMR: (300 MHz, CDCl₃): 7.10 (t,1H, J=7.5 Hz); 7.00 (d, 1H, J=8.4 Hz); 6.78 (m, 2H); 6.60 (d, 1H, J=9Hz); 4.10 (s, 2H); 3.84 (m, 8H); 2.93 (t, 1H, J=12.9 Hz).

8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinolinehydrobromide (8).

The crude 7 (0.834 g; 3.0 mmol) was dissolved in 50 ml of anhydrousdichloromethane. The solution was cooled to −78° C. and 15.0 ml of aboron tribromide solution (1.0 M in dichloromethane) was slowly added.The solution was stirred overnight, while the reaction slowly warmed toroom temperature. The solution was recooled to −78° C., and 50 ml ofmethanol was slowly added to quench the reaction. The solution was thenconcentrated to dryness. Methanol was added and the solution wasconcentrated. This process was repeated three times. The resulting brownsolid was treated with activated charcoal and recrystallized fromethanol: mp 298-302° C. dec; ¹H NMR: (300 MHz, D₂O): 7.32 (t, 1H, J=6.6Hz); 7.13 (d, 1H, J=8.4 Hz); 7.04 (d, 1H, J=8.4 Hz); 4.37 (m, 2H); 4.20(t, 3H, J=10 Hz). Anal. Calc'd for C₁₅H₁₄BrNO₃.H₂O: C, 50.87; H, 4.55;N, 3.82. Found: C, 51.18; H, 4.31; N, 3.95.

N-allyl-8,9-dimethoxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinoline(10).

Tetrahydroisoquinoline 7 (1.273 g; 4.5 mmol) was dissolved in 150 ml ofacetone. Potassium carbonate (0.613 g; 4.5 mmol) and 0.4 ml (4.6 mmol)of allyl bromide were added. The reaction was stirred at roomtemperature for four hours. The solid was then removed by filtration andwashed on the filter several times with ether. The filtrate wasconcentrated and purified by flash chromatography (silica gel, 50% ethylacetate:hexane) to give 1.033 g (71%) of a yellow oil that was usedwithout further purification: ¹H NMR: (300 MHz, CDCl₃): 7.15 (t, 1H, J=9Hz); 7.04 (d, 1H, J=9 Hz); 6.83 (m, 2H); 6.65 (d, 1H, J=6 Hz); 5.98 (m,1H); 5.27 (m, 2H); 4.10 (m, 3H); 3.95 (s, 3H); 3.86 (s, 3H); 3.46 (d,1H, J=15 Hz); 3.30 (d, 2H, J=6 Hz); 2.56 (t, 1H, J=12 Hz).

N-allyl-8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinoline(11).

N-Allyl amine 10 (0.625 g; 1.93 mmol) was dissolved in 50 ml ofdichloromethane. The solution was cooled to −78 ° C. and 10.0 ml of BBr₃solution (1.0 M in dichloromethane) was slowly added. The solution wasstirred overnight, while the reaction slowly warned to room temperature.After recooling the solution to 78° C., 50 ml of methanol was slowlyadded to quench the reaction. The reaction was then concentrated todryness. Methanol was added and the solution was concentrated. Thisprocess was repeated three times. Recystallization of the brown solidfrom ethanol gave 0.68 g (61%) of a white solid: mp 251-253° C. dec; ¹HNMR: (300 MHz, D₂O): 10.55 (s, 1H); 10.16 (s, 1H); 8.61 (t, 1H, J=9 Hz);8.42 (d, 1H, J=9 Hz); 8.31 (d, 1H, J=9 Hz); 7.87 (d, 1H, J=9 Hz); 7.82(d, 1H, J=9 Hz); 7.36 (q, 1H, J=9 Hz); 6.89 (m, 2H); 6.85 (d, 1H, J=15Hz); 5.58 (m, 3H); 5.28 (m, 2H); 3.76 (d, 1H, J=3 Hz). HRCIMS m/z:Calc'd: 295.1208; Found: 295.1214.

N-propyl-8,9-dimethoxy-1,2,3,11b-tetrahydrochromeno-(4,3,2-de)-isoquinoline(12).

N-Allyl amine 10 (1.033 g; 3.2 mmol) was dissolved in 50 ml of ethanol.Palladium on charcoal (10% dry; 0.103 g) was then added. The mixture wasshaken on a Parr hydrogenator under 60 psi H₂ for 3 hours. After TLCshowed no more starting material, the mixture was filtered throughCelite and concentrated to give 0.95 g (91%) of an oil that was usedwithout further purification: ¹H NMR: (300 MHz, CDCl₃): 7.15 (t, 1H,J=7.2 Hz); 7.04 (d, 1H, J=8.1 Hz); 6.84 (t, 2H, J=7.5 Hz); 6.65 (d, 1H,J=8.4 Hz); 4.07 (m, 2H); 3.95 (s, 3H); 3.86 (s, 3H); 3.71 (q, 1H, J=5.1Hz); 3.42 (d, 2H, J=15.6 Hz); 2.62 (m, 2H); 2.471 (t, J=10.5 Hz); 1.69(h, 2H, J=7.2 Hz); 0.98 (t, 3H, J=7.5 Hz). CIMS m/z: 326 (M+H⁺, 100%).

N-propyl-8,9-dihydroxy-1,2,3,11b-tetrahydrochromeno[4,3,2-de]isoquinoline(13).

The N-propyl amine 12 (0.90 g; 2.8 mmol) was dissolved in 200 ml ofdichloromethane and cooled to −78° C. In a separate 250 ml round bottomflask, 125 ml of dry dichloromethane was cooled to −78° C., and 1.4 ml(14.8 mmol) of BBr₃ was added via syringe. The BBr₃ solution wastransferred using a cannula to the flask containing the startingmaterial. The solution was stirred overnight, while the reaction slowlywarmed to room temperature. After recooling the solution to −78° C., 50ml of methanol was slowly added to quench the reaction. The reaction wasthen concentrated to dryness. Methanol was added and the solution wasconcentrated. This process was repeated three times. The resulting tansolid was suspended in hot isopropyl alcohol. Slowly cooling to roomtemperature resulted in a fine yellow precipitate. The solid wascollected by filtration (0.660 g; 63%): mp 259-264° C. dec; ¹H NMR: (300MHz, CDCl₃): 7.16 (t, 1H, J=9 Hz); 6.97 (d, 1H, J=12 Hz); 6.83 (d, 1H,J=9 Hz); 6.55 (d, 1H, J=9 Hz); 6.46 (d, 1H, J=9 Hz); 4.45 (d, 1H, J=15Hz); 4.10 (m, 3H); 3.17 (q, 2H, J=6 Hz); 3.04 (t, 1H, J=9 Hz); 1.73 (q,2H, J=9 Hz); 0.90 (t, 3H, J=6 Hz). Anal. Calc'd. for C₁₈H₂₀BrNO₃: C,57.16; H, 5.33; N, 3.70. Found: C, 56.78; H, 5.26; N, 3.65.

Pharmacology of Dinoxyline

Methods: Radioreceptor Studies in Brain Tissue

Frozen rat striata was homogenized by seven manual strokes in a WheatonTeflon-glass homogenizer in 8 ml ice cold 50 mM HEPES buffer with 4.0 mMMgCl₂, (pH 7.4). The tissue was centrifuged at 27,000×g for 10 min, thesupernatant was discarded, and the pellet was homogenized (5 strokes)and resuspended in ice cold buffer and centrifuged again. The finalpellet was suspended at a concentration of approximately 2.0 mg wetweight/ml. The amount of tissue added to each assay tube was 1.0 mg, ina final assay volume of 1.0 ml. D₁ receptors were labeled with [³H]SCH23390 (0.30 nM). D₂ receptors were labeled with [³H] spiperone (0.07nM); unlabeled ketanserin (50 nM) was added to mask binding to 5HT₂sites. Total binding was defined as radioligand bound in the absence ofany competing drug. Nonspecific binding was estimated by addingunlabeled SCH23390 (1 μM) or unlabeled chlorpromazine (1 M) for D₁ andD₂ receptor binding assays, respectively. Triplicate determinations weremade for each drug concentration in each assay. Assay tubes wereincubated at 37° C. for 15 minutes. Binding was terminated by filteringwith ice cold buffer on a Skatron 12 well cell harvester (Skatron, Inc.,Sterling, Va.) using glass fiber filter mats (Skatron no. 7034). Filterswere allowed to dry and 2.0 ml of Optiphase HI-SAF II scintillationfluid was added. After shaking for 30 minutes, radioactivity wasdetermined on a LKB Wallac 1219 RackBeta liquid scintillation counter(Wallac, Gaithersburg, Md.). Tissue protein levels were estimated usingthe BCA protein assay reagent.

Functional Studies in Brain Tissue

Frozen striatal tissue (ca. 40 mg) was homogenized in 4 ml of buffer (5mM Hepes, 2 mM EGTA, pH 7.5) using 10 strokes in a Wheaton Teflon-glasshomogenizer. Four ml of 50 mM Hepes with 2 mM EGTA buffer (pH 7.5) wasadded, and the tissue was homogenized by an additional 3 strokes. A 20μl aliquot of this tissue homogenate was added to a prepared reaction.The reaction mixture consisted of 100 mM Hepes (pH 7.4), 100 mM NaCl, 4mM MgCl₂, 2 mM EDTA, 500 μM isobutyl methylxanthine (IBMX), 0.01%ascorbic acid, 10 μM pargyline, 2 mM ATP, 5 μM GTP, 20 mMphosphocreatine, 5 units of creatine phosphokinase (CPK), and selectedconcentrations of DA. The final reaction volume was 100 μl. Basal cAMPactivity was determined by incubation of tissue in the reaction mixturewith no drug added. Tubes were assayed in duplicate. After a 15 minincubation at 30° C., the reaction was stopped with the addition of 500μl of 0.1 N HCl. Tubes were vortexed briefly, and then spun in a BHGHermle Z 230 M microcentrifuge for five min at 15,000×g to eliminatelarge particles.

The concentration of cAMP in each sample was determined with an RIA ofacetylated cAMP, modified from that previously described (Harper andBrooker, 1975). Iodination of cAMP was performed using a methoddescribed previously (Patel and Linden, 1988). Assay buffer was 50 mMsodium acetate buffer with 0.1% sodium azide (pH 4.75). Standard curvesof cAMP were prepared in buffer at concentrations of 2 to 500fmoles/assay tube. To improve assay sensitivity, all samples andstandards were acetylated with 10 μl of a 2:1 solution oftriethylamine:acetic anhydride. Samples were assayed in duplicate. Eachassay tube contained 100 μl of diluted sample, 100 μl of primaryantibody (sheep, anti-cAMP, 1:100,000 dilution with 1% BSA in buffer)and 100 μl of [¹²⁵I]-cAMP (50,000 dpm/100 μl of buffer); total assayvolume was 300 μl. Tubes were vortexed and stored at 4° C. overnight(approx. 18 hr). Antibody-bound radioactivity was then separated by theaddition of 25 μL of BioMag rabbit, anti-goat IgG (Advanced Magnetics,Cambridge Mass.), followed by vortexing and further incubation at 4° C.for 1 hr. To these samples 1 ml of 12% polyethylene glycol/50 mM sodiumacetate buffer (pH 6.75) was added and all tubes were centrifuged at1700×g for 10 min. Supernatants were aspirated and radioactivity in theresulting pellet was determined using an LKB Wallac gamma counter(Gaithersburg, Md.).

Radioreceptor Studies with Expressed Receptors

Radioreceptor and function studies were also conducted for cloned humanor monkey receptors transfected into one of several cell lines [e.g.,C-6 glioma or Chinese hamster ovary (CHO) cells]. Cells were grown inappropriate medium, and at confluency, harvested for membranepreparation. Flasks of cells in the same passage were scraped using arubber policeman and collected in 50 ml centrifuge tubes. These werespun for 10 min at 1200×g, to pellet whole cells. The supernatant wasdiscarded and then five ml of PBS (phosphate buffered saline)/flask wasadded to the centrifuge tubes to resuspend the cells. The tubes werethen centrifuged again for min at 28,500×g. The PBS was removed and thepellet suspended in a solution of 10% DMSO in PBS. Cells werehomogenized with a polytron for 10 seconds on setting 5. One ml aliquotswere stored at −80° C. until use in receptor binding studies. Aliquotscontained approximately 1 mg/ml of protein, as measured using the BCAprotein assay reagent (Pierce, Rockford, Ill.).

For D₁-like receptors, membrane protein (50-75 g was incubated with eachtest compound and [³H] SCH23390 (0.3 nM) in 50 mM Tris-HCl (pH 7.4),with 120 mM NaCl, 5 mM KCl, 2 mM CaCl₂ and 1 mM MgCl₂. SCH23390 (5 μM)was used to define nonspecific binding. Tubes were run in triplicate ina final volume of 500 μl. After incubation for 30 minutes at 37° C.,tubes were filtered rapidly through Skatron glass fiber filter mats(11734), and rinsed with 5 ml of ice-cold wash buffer (50 mM Tris, pH7.4) using a Skatron Micro Cell Harvester (Skatron Instruments Inc.,Sterling, Va.). Filters were allowed to dry, then punched intoscintillation vials (Skatron Instruments Inc., Sterling, Va.). OptiPhase‘HiSafe’ II scintillation cocktail (1 ml) was added to each vial. Aftershaking for 30 min, radioactivity in each sample was determined on anLKB Wallac 1219 Rackbeta liquid scintillation counter (Wallac Inc.,Gaithersburg, Md.). A similar protocol was used for D₂-like receptors,except that [³H] spiperone (0.07 nM) was used as the radioligand.

Functional Studies with Expressed Receptors

Agonist intrinsic activity was assessed by the ability of selectedcompounds to stimulate adenylate cyclase, as measured by cAMP formationin whole cells. In C-6 cells, for example, the dose response curve foreach drug was fit using a sigmoid function to determine maximaleffective concentration (top plateau of curve) as well as EC₅₀s. Alldrugs were run in the same assay in order to decrease variability acrosscell passages. Confluent plates of cells were incubated with drugsdissolved in DMEM-H plain media supplemented with 20 mM Hepes, 0.01%ascorbic acid and 500 μM iso-butyl-methyl xanthine (IBMX; pH 7.2; mediaA). The final volume for each well was 500 μl. In addition to the doseresponse curves run for each drug, basal levels of cAMP andisoproterenol-stimulated (through endogenous β₂ receptors, positivecontrol) cAMP levels were evaluated for each plate. Each condition wasrun in duplicate wells. Following a 10 min incubation at 37° C., cellswere rinsed briefly with media, and the reaction stopped with theaddition of 500 μl 0.1 N HCl. Cells were then allowed to chill for 5-10min at 4° C., the wells were scraped and the volume placed into 1.7 mlcentrifuge tubes. An additional 1 ml of 0.1 N HCl was added to eachtube, for a final volume of 1.5 ml/tube. Tubes were vortexed briefly,and then spun in a BHG Hermle Z 230 M microcentrifuge for five min at15,000×g to eliminate large cellular particles. Cyclic AMP levels foreach sample were determined as described above.

Data were calculated for each sample, and expressed initially aspmol/mg/min cAMP. Baseline values of cAMP were subtracted from the totalamount of cAMP produced for each drug condition. To minimize interassayvariation, a reference compound (DA; 100 μM) was included in each assayto serve as an internal standard that allowed normalization of the data.Data for each drug were expressed relative to the percentage of thestimulation produced by 100 M DA. Normalized dose-response curves wereanalyzed by nonlinear regression using an algorithm for sigmoid curvesin the curvefitting program InPlot (Graphpad, Inc.; San Francisco,Calif.). For each curve, the program provided point estimates of boththe EC₅₀ and the maximal stimulation produced (i.e., top plateau ofsigmoid curve).

Additional Claimed Variations of the Subject Compounds

Using the same general procedures described in Example 1 above, thecompounds of Examples 1-56 as set forth in Table II below aresynthesized using starting compounds corresponding to those illustratedin Scheme 1, but substituted with functional groups appropriate toprovide the substitution patterns depicted on the fusedchromenoisoquinoline product shown for each Example. Thus, for example,6, 7 and/or 8 substituted analogs of compound 3 (scheme 1) provide thecorresponding substituents R₆, R₅, and R₄, respectively, on Formula I.Use of other 1 and 3 substituted isoquinolines (analogs of compound 3 inscheme 1) provided corresponding substitution patterns at C₃ and C₁ inFormula I.

Example Number R₁ R₂ R₃ R₄ R₅ R₆ R₈ X₉   1B H H H CH₃ H H H OH  2 H H HH CH₃ H H OH  3 H H H H H CH₃ H OH  4 H H H C₆H₅ H H H OH  5 CH₃ H CH₃CH₃ H H H OH  6 H H C₃H₇ H CH₃ H H OH  7 H H H C₂H₅ H H H OH  8 H H H HC₂H₅ H H OH  9 H H H H CH₃ CH₃ H Cl 10 CH₃ H C₃H₇ CH₃ CH₃ H H OH 11 CH₃H C₂H₅ H CH₃ CH₃ H Cl 12 CH₃ H CH₃ H H C₂H₅ H OH 13 CH₃ H C₄H₉ H OH H HOH 14 H H H CH₃ OH H H OH 15 H H H H F H H OH 16 H H H OH H H H Cl 17 HH H Br H H H OH 18 H CH₃ H H Br H H OCH₃ 19 H CH₃ H H H Br H OCH₃ 20 HCH₃ H CH₃ Br H H OCH₃ 21 CH₃ H CH₃ F H H H OH 22 CH₃ H CH₃ H F H H OH 23CH₃ H CH₃ H H F H OH 24 C₂H₅ H C₂H₅ H OH H H F 25 C₂H₅ H C₂H₅ CH₃ OH H HF 26 C₂H₅ H C₂H₅ CH₃O H CH₃ H F 27 C₃H₇ H C₃H₇ H CH₃O H H Cl 28 C₃H₇ HC₃H₇ H CH₃ CH₃O H Cl 29 C₃H₇ H C₃H₇ C₂H₅O H H H OH 30 C₃H₇ H C₃H₇ H H OHH OH 31 C₄H₉ H C₄H₉ CH₃ H H H OH 32 C₄H₉ H C₄H₉ H OH CH₃ H OH 33 C₄H₉ HC₄H₉ OH Cl H H OH 34 C₄H₉ H C₄H₉ OH Cl H H OH 35 H H H H H H H H 36 H HH CH₃ H H H H 37 H H H H CH₃ H H H 38 H H H H H CH₃ H H 39 H H H H H HCH₃ OH 40 H H H H H H CH₂(CH₃)₂ OH 41 H H H H H H CH₃ H 42 H H H H H HCH₂(CH₃)₂ H 43 H H H CH₃ H H CH₃ OH 44 H H H H CH₃ H CH₃ OH 45 H H H H HCH₃ CH₃ OH 46 H H H H H H CH₂CH₃ OH 47 H C₃H₅ H H CH₃ H H OH 48 H C₃H₅ HH H H OH H 49 H C₃H₅ H H H H H OCH₃ 50 H C₃H₅ H H C₂H₅ H H OH 51 H C₃H₅H CH₃ H OCH₃ H OH 52 H C₃H₅ H H H H H OCH₃ 53 H C₃H₅ H H CH₃ H H OCH₃ 54H C₃H₅ H H H H H OH 55 H C₃H₅ H H C₂H₅ H H OH 56 H C₃H₅ H OCH₃ H C₂H₅ HOH

The foregoing examples are illustrative of the invention and are notintended to limit the invention to the disclosed compounds. Variationsand modifications of the exemplified compounds obvious to one skilled inthe art are intended to be within the scope and nature of the inventionas specified in the following claims.

1. A method for treating a patient having a dopamine-related dysfunctionof the central nervous system selected from the group consisting ofattention deficit disorder, attention-deficit hyperactivity disorder,narcolepsy, cognitive disorders, memory disorders, schizophrenia,substance abuse disorders, and negative symptoms of schizophrenia, saidmethod comprising the step of administering to said patient in needthereof an effective amount of a compound of the formula:

which activates both D₁ and D₄ dopamine receptors.
 2. The method ofclaim 1 wherein the compound administered binds to both D₁ and D₄dopamine receptors with a K_(0.5) of less than about 1 μM.
 3. A methodfor treating a patient having a dopamine-related dysfunction of thecentral nervous system selected from the group consisting of attentiondeficit disorder, attention-deficit hyperactivity disorder, narcolepsy,cognitive disorders, memory disorders, schizophrenia, substance abusedisorders, and negative symptoms of schizophrenia, said methodcomprising the step of administering to said patient in need thereof aneffective amount of a compound of the formula:

which activates both D₁ and D₄ dopamine receptors; wherein: R₁, R₂ andR₃ are hydrogen, C₁-C₄ alkyl, or C₂-C₄ alkenyl; R₈ is hydrogen, C₁-C₄alkyl, or a phenoxy protecting group; X₉ is hydrogen, halo, or a groupof the formula —OR wherein R is hydrogen, C₁-C₄ alkyl, or a phenoxyprotecting group, and further when X₉ is a group of the formula —OR, thegroups R and R₈ can be taken together to form a group of the formula—CH₂—; R₄, R₅, and R₆, are independently selected from the groupconsisting of hydrogen, C₁-C₄ alkyl, phenyl, halo, or a group —ORwherein R is as defined above; or a pharmaceutically acceptable saltthereof.
 4. The method of claim 3 wherein X₉ is hydroxy and R₈ ishydrogen.
 5. The method of claim 3 wherein R₁, R₂, and R₃ are hydrogen.6. The method of claim 4 wherein R₁, R₂, and R₃ are hydrogen.
 7. Themethod of claim 3 wherein R₁, R₃, R₄, R₅ and R₆ are each hydrogen. 8.The method of claim 3 wherein X₉ and R₈ are hydrogen.
 9. The method ofclaim 3 wherein R₁ and R₃ are hydrogen.
 10. The method of claim 3wherein R₁ and R₃ are C₁-C₄ alkyl.
 11. The method of claim 3 wherein R₂is C₁-C₄ alkyl or C₂-C₄ alkenyl.
 12. The method of claim 3 wherein thecompound administered binds to both D₁ and D₄ dopamine receptors with aK_(0.5) of less than about 1 μM.